1. Field of the Invention
This invention relates to a runner assembly for an umbrella frame, more particularly to a runner assembly with a tubular thrust member which is operable to move a runner between upper and lower positions, and to retain the runner in the upper position.
2. Description of the Related Art
Referring to FIG. 1, a conventional runner assembly of an umbrella frame disclosed in U.S. Pat. No. 6,758,229 is shown to include a runner 2 which is slidable on a central shaft 1 that is formed with a protuberance having a shoulder 101, and a sleeve member 3 which surrounds and which is movable relative to the runner 2. The runner 2 has two radially biased retaining members 201 which can be depressed by a cam surface 301 of the sleeve member 3 so as to be retained on the shoulder 101 to thereby arrest the runner 2 in an opened position.
Referring to FIG. 2, another conventional runner assembly of an umbrella frame disclosed in U.S. Pat. No. 7,281,542 is shown to include a runner 4, two engaging slices 5 pivotally connected on the runner 4, and a sleeve 6 displaceably disposed around the runner 4. Each of the engaging slices 5 has a middle pivot portion 501 which is engaged with a groove 402 in the runner 4 such that an engaging end 502 thereof is pressed by an inner ring 601 into a hole 401 in the runner 4 to be retained on a shoulder of a central shaft (not shown) so as to keep the umbrella in an open state.
It is desirable to improve the aforesaid runner assembly to simplify the structure thereof, to render the same suitable for any known umbrella frames, and to permit a runner to be retained firmly on a shaft in an upper position.